Inspired by this great answer.
There is a planet with:
- Floatium, a superconductor that behaves as such at 0 ºC and is found in nature.
- A stronger magnetic field than Earth's.
In really cold areas I imagine people seeing that Floatium floats after being impacted by a lightning. After that they would try to take big rocks of that material, force a lightning to land on them (maybe through metal rods) and build their cities there.
Would it be plausible to create floating cities this way?
I'm afraid that maybe the force needed to push the rock up would be too much to be really feasable. Or that the whole thing doesn't have any sense.
I'm interested also in how low the technology level can be and still those floating cities be possible.
PS: An alternative which seems viable had been asked in v2 of this scenario, thanks to Karls' answer.